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Biomedical subjects

M Takumida

Publications and source records attributed to M Takumida.

At least 73 records · Page 4Linked to original sources
PubMed1989

Glycocalyx and ciliary interconnections of the vestibular end organs: an investigation by high-resolution scanning electron microscopy.

The ultrastructure of the glycocalyx and ciliary interconnections was investigated by using a tannic acid staining technique. A high-resolution scanning electron microscope was used for the observation. The plasma membrane showed a rather rough appearance which was most prominent in the ciliary membrane of the sensory cells. Ciliary interconnections emerged from the plasma membrane and tightly connected neighboring cilia. The tip links stretched from the tips of the stereocilia to their taller neighbors. These tip links were arranged in the same direction towards the kinocilium. These findings indicate that the ciliary interconnections may keep the cilia arranged in a bundle, and the tip links may be involved in a sensory cell transduction system.

Animals↗
PubMed1989

Carbohydrates of the vestibular end organs detected by lectins.

The presence of carbohydrates was investigated in the vestibular end organs of the guinea pig using FITC-lectins. The following sugars have been identified: N-acetyl-glucosamine, galactose, mannose and fucose. In contrast, N-acetyl-galactosamine was not clearly detected. These sugars were suggested to be closely related to the formation and maintenance of otoconia as well as of the cupula. N-acetyl-glucosamine was considered to be the major component of the glycocalyx and also suggested to have a function as an anchoring structure between the epithelial cell and the otolithic membrane or the cupula.

Animals↗
PubMed1989

Effect of acetazolamide (Diamox) on the endolymphatic sac.

The effect of acetazolamide on the ultrastructures of the murine endolymphatic sac was investigated. The animals were given a single intravenous dose of acetazolamide (100 mg/b.w.) and were sacrificed 0, 15, 30, 60 and 120 min after the injection, respectively. Prominent changes in the fine structure of the epithelial cells could be observed after 30 min. These alterations were even more pronounced after 1 h. After 2 h, the normal cell structure became to be reestablished. The most conspicuous change was a general reduction in the electron density of the dark cells. This was accompanied with a decreased number of cell organelles, especially ribosomes. Some light cells also underwent temporal modifications in their structure in the form of a reduced nuclear stainability associated with a loss of pinocytotic vesicles near the apical plasmalemma. In general, the dark cells seemed to be more influenced by acetazolamide than the light cells. The possibility that the dark cell changes are related to a modification of transepithelial ion and water flow is discussed.

Acetazolamide↗
PubMed1989

Sensory hair fusion and glycocalyx changes after gentamicin exposure in the guinea pig.

This study demonstrates the mechanism of sensory hair fusion and its relationship to glycocalyx on the inner ear sensory cells of gentamicin-treated guinea pigs, using the ruthenium red staining technique. 0.5 ml containing 5 mg gentamicin sulfate solution was injected in a single dose into the middle ear. After 7 days, various stages of sensory hair degeneration could be observed. The glycocalyx was clearly visualized by ruthenium red. The degeneration starts with a decrease in or even complete loss of glycocalyx in the sensory hairs, with subsequent local adhesion of the plasma membrane in neighbouring hairs. These findings suggest that the glycocalyx of the sensory cell may play an important role in separating the cilia, yet keeping them in a bundle.

Animals↗
PubMed1989

The effects of glycerol on vestibular function and the endolymphatic sac after pre-treatment with colchicine.

The endolymphatic sac (ES) is believed to absorb endolymph. Recent studies have suggested that the ES also has a secretory capacity, a function that may be related to the regulation of inner ear fluid volume and pressure. Other studies indicate that hyperosmolar substances, such as glycerol and urea, may initiate a secretion of glycoprotein into the ES. This function was suggested to be related to a regulatory function of the ES by which it can compensate for a decrease in endolymph pressure. In order to investigate this regulatory potential of the ES, the effect of glycerol on the ES was investigated with or without the presence of pharmacological inhibition of glycoprotein secretion through colchicine treatment. Animals treated in such a way showed marked signs of impaired inner ear function, including loss of postural control and loss of Preyer's reflex. Significant ultrastructural changes were noted in the endolymphatic sac suggesting a disturbed secretory activity. The results may indicate that the endolymphatic sac may actively respond to changes in endolymph homeostasis through secretion of macromolecular substances and that alterations in this secretion may lead to functional disturbances of the inner ear.

Animals↗
PubMed1989

Observation of the glycocalyx of the organ of Corti: an investigation by electron microscopy in the normal and gentamicin-treated guinea pig.

The ultrastructure of the glycocalyx of the organ of Corti in the normal and gentamicin-treated guinea pig was investigated at the electron microscopic level by using the ruthenium red staining technique. The glycocalyx was evident over the whole apical surface of both sensory and supporting cells. The entire length of the stereocilia of both inner and outer hair cells was seen to be covered by a glycocalyx, which interconnected the neighbouring stereocilia. In the gentamicin-treated animals, the fusion process between the stereocilia was revealed and a decrease of the glycocalyx was noticed at the point where fusion started. These findings suggest that the glycocalyx may play an important role in holding the stereocilia together in a bundle, yet prevent their close contact by means of its strong negative charge.

Animals↗
PubMed1988

The basement membrane and associated structures in the murine endolymphatic sac.

The ultrastructure of the basement membrane of the murine endolymphatic sac was studied under various experimental conditions in labyrinthectomized and ethacrynic acid-treated animals and was compared with normal anatomy. The basement membrane was clearly visualized after staining with ruthenium red or dialyzed iron. The basement membrane of the murine sac consists of two different layers: the lamina rara and the lamina densa. It demarcates the border between the epithelial cells and the subepithelial connective tissue. Our findings suggest that the basement membrane acts as a physical support to the epithelium in the endolymphatic sac. The basement membrane also shows a dynamic capacity to form a new basement membrane, with the result that the lateral intercellular space between contiguous epithelial cells may be integrated with the subepithelial space. This system is believed to act as a macromolecular and bulk water transport system. In the subepithelial space, collagen, reticular and elastic fibrils are found having a close relationship to the basement membrane. The elastic fibres are presumed to play a role in the pressure-regulating mechanism in the endolymphatic sac.

Animals↗
PubMed1988

Ruthenium red staining of the endolymphatic sac in the guinea pig.

The ultrastructure of the guinea pig endolymphatic sac was studied, using the ruthenium red staining technique. The dye stained the apical cell surface coat and the homogeneous substance in the luminal space of the endolymphatic sac, when introduced from the luminal side of the epithelium. It is suggested that the surface coat and homogeneous substance may play an important part in the endolymph regulatory mechanism in the endolymphatic sac. When ruthenium red was introduced from the subepithelial side, the basolateral surface of the epithelial cells usually became brightly stained in the absence of staining of the apical cell surface, due to the presence of the tight junctions. In some instances, however, the dye penetrated beyond the level of the tight junctions. Pinocytotic vesicles and larger vacuoles in the epithelial cells were also sometimes stained, both apically and near the lateral cell surface. These findings suggest that endolymph efflux mechanisms in the endolymphatic sac may involve the combined actions of a paracellular and transepithelial flow as well as a transcellular, vacuolar bulk flow.

Animals↗
PubMed1988

Ultrastructural localization of carbonic anhydrase and its possible role in the endolymphatic sac.

Carbonic anhydrase was detected histochemically in the guinea pig endolymphatic sac. The enzyme reaction was positive in both light and dark epithelial cells. In the former, the reaction product was found in the cytoplasm, especially around the intracytoplasmic vesicles and vacuoles. Reaction product was found in the basolateral infoldings as well. The dark epithelial cells also displayed carbonic anhydrase activity in the cytoplasm as well as in the lysosome-like bodies. It is suggested that this enzyme may be involved in (1) ionic or fluid regulation of the endolymph, (2) otoconia metabolism, and (3) phagocytotic activities.

Animals↗
PubMed1988

The glycocalyx of inner ear sensory and supporting cells.

The ultrastructure of the glycocalyx of the sensory and the supporting cells of guinea pig inner ear was studied using the ruthenium red staining technique. The glycocalyx was found over the entire length of the stereocilia and the kinocilium of the sensory cells as well as over the entire apical surface of the supporting cells appearing as a fuzzy filamentous layer. The mechanism of sensory hair fusion and its relationship to glycocalyx in gentamicin treated animals was also studied. The sensory hair degeneration process started with a decrease or even a loss of glycocalyx ensued by a local attachment of neighbouring sensory hairs. These findings have led to two hypotheses about the function of the glycocalyx of the sensory hairs. Firstly the glycocalyx serves as anchoring structure for the mechanical coupling between the ciliary structures so that when a single hair in the bundle is deflected, all stereocilia and kinocilium within that bundle move in unison as a group. Secondly, because of the electronegativity of its acidic groups, the glycocalyx serves to maintain, by repulsion, a distance between adjacent cilia, preventing close contact and preventing the cell membranes from fusing.

Animals↗
PubMed1987

Three-dimensional ultrastructure of the endolymphatic sac.

The subcellular structures of the epithelial cells of the guinea pig endolymphatic sac were studied. By using a newly developed scanning electron microscopy technique, the intracellular organelles could be studied three-dimensionally and the topographic relationships analyzed. The light epithelial cell has an extensive network of endoplasmic reticulum which is characteristically arranged in a baso-apical direction. The connections between the inner surface of the plasmalemma and the endoplasmic reticulum were observed, as were connections between the Golgi complex and the endoplasmic reticulum. Our findings support the hypothesis that the endoplasmic reticulum might form transcellular channels through which the cell can transport water and ions from the lumen of the endolymphatic sac out into the subepithelial tissue. The dark epithelial cells seen in particular contained the smooth type of endoplasmic reticulum. Lysosomes were also observed in the dark cells, indicating that these cells probably have more of a secretory function.

Animals↗
PubMed1986

Inner ear damage induced by Mycobacterium fortuitum.

We used electron microscopy to investigate Mycobacterium fortuitum-induced changes in the inner ears of mice. We found that the inner and outer hair cells had degenerated and disappeared in the organ of Corti. Changes in the lower turn of the cochlea were more severe than those of the upper turn while the changes of the outer hair cells were more severe than those of the inner hair cells. Disappearance, fusion and ballooning of the sensory hairs were observed in the vestibular organs. The bacterial extract also induced inner ear damage which was similar to that caused by live M. fortuitum.

Animals↗
PubMed1986

Development of the crista ampullaris in the mouse.

The process of development of the crista ampullaris has been investigated in the mouse using SEM. Cristae ampullaris of the CBA/CBA mice, from the 13.5th gestational day to the day 2 weeks by were studied. On the 13.5th gestational day, there were numerous microvilli and a primary cilium on the crista ampullaris. Sensory hairs first appeared on the 14.5th gestational day. The kinocilium and stereocilia were short and the length of the stereocilia was almost constant. The formation of the cupula, which had fine network-like structures, started on the 14.5th gestational day.

Animals↗
PubMed1986

Neurilemmoma of the larynx: (a case report).

The authors have treated a 61-year-old woman with neurilemmoma of the larynx. The tumour was located in the submucosal region of the arytenoid on the right side of the larynx. Surgical resection of the tumour had to be done by external neck excision instead of endoscopically.

Female↗
PubMed1986

Scanning electron microscopic observation of the crista ampullaris.

The crista ampullaris of the guinea pig and the bull frog were investigated by scanning electron microscopy. The crista ampullaris were freeze fractured or sheared followed by maceration with 0.1% OsO4 solution. Following this, three-dimensional intracellular structures were observed. The mitochondria of the sensory cells varied in shape from globular to long and slender. Golgi apparatus and endoplasmic reticulum of the sensory cells were also demonstrated clearly. Nerve elements, nerve endings and synaptic structures were also observed stereoscopically.

Animals↗